Our copending application Ser. No. 155,108 filed June 21, 1971, now U.S. Pat. No. 3,839,032, discloses a method and apparatus for the making of electrostatic prints of an original by a contact transfer method. More particularly in the system disclosed in the copending application a photoconductive surface such as that formed on a drum first is moved past a corona which applies a uniform electrostatic charge over the surface moving thereby. Next the charged surface is exposed to an image of the original to cause the charge to leak off in areas which are not to be developed. The resultant latent electrostatic image is then subjected to the action of a liquid developer made up of particles of a relatively tacky toner suspended in a light hydrocarbon carrier liquid. When the image has been developed, it is transferred onto a sheet or length of copy material by pressing the copy material against the image-bearing surface. Owing to the greater affinity of the tacky toner for the copy material than for the photoconductor surface the image is transferred onto the copy material.
Proper transfer of the developed image from the photoconductive surface to the copy material requires that no excess developer liquid be present in the region at which the transfer takes place. Moreover, if pollution of the surrounding atmosphere is to be avoided excess hydrocarbon liquid should be removed from the surface as soon after development as is possible. Various systems have been proposed for removing the excess developer liquid from the developed-image-bearing photoconductive surface. Our copending application Ser. No. 200,433 filed Nov. 19, 1971, now U.S. Pat. No. 3,741,643, discloses a Pneumatic Assembly for Removing Excess Developer Liquid from Photoconductive Surfaces. More particularly, that copending application discloses and claims an air knife for directing a stream of air against the developed-image-bearing surface to drive excess liquid back toward the overflow tray of the developer unit. As is pointed out in the copending application one of the problems which has risen in excess developer liquid removal systems is the tendency of the excess developer removal unit to collect particles of toner which cause a buildup which after a period of time in use of the machine renders the cleaning system ineffective. While the system shown in our copending application effectively removes excess developer liquid from an image-bearing photoconductive surface it is not as effective as is desirable. Moreover it requires the provision of a blower for producing air under pressure to feed the air knife. It further tends to pollute the air within the machine cabinet.
We have invented an improved system for removing excess developer liquid from a photoconductive surface. Our system removes excess liquid from the developed-image-bearing surface without disturbing the image. Our improved system removes such a substantial amount of excess liquid as to minimize the possibilities of pollution. It does not require any separate supply of compressed air. It will operate for a relatively long period of time without maintenance. It is relatively simple in construction for the result achieved thereby.